We’ve had a long-standing (unfortunately private) internal ticket for implementing a Credentials should not be hard-coded rule for PL/SQL.
Because the credentials in question are generic and not linked to a specific provider, our shiny new “secret detection” rules don’t flag these instances as issues. However, I agree that this is an important gap.
I’ve linked your post to the existing ticket to increase its visibility, and I’ll also bring this up with our product managers.